As part of the spammers "banning" process, I can chose to "remove all posts" as well. If they've spammed excessively, it can be easier to do that than go through all their posts one at a time and move / delete them.
I think I was on my mobile when I saw the last spam attack and chose the "remove all posts" option. That sometimes leaves posts that make no sense as the thread remains, but the first spam post goes.
I'll clean them all up in a bit - if anyone spots one, then just "report" it using the ! button and it'll flag it up to us quickly. k: